I think everyone should have the right to do what they want with their bodies. If they choose to get a piercing, a tattoo, do scarification, get implants, get plastic surgery then that's their choice. They're all ways to modify the body as a form of self expression though sometimes they are done to change the reaction of the people around them.
Visible tattoos and facial piercings are often done to shock parents and friends and their community in general. But it might also be that the person truly enjoys these pieces of expression. It's just as expressive as the clothes they choose to wear.
Unnecessary plastic surgery and implants are often done to increase attractiveness (though the person doing it just needs a self esteem boost, not surgery).
I have my ears pierced and that's the only piercing I'll ever get and one day I hope to get a tattoo of a tree on my back. My sister has multiple piercings and tattoos.